If the fan and light is coming on inside the oven then its more then likely the heater element at fault here.
Remove the back panel inside the oven and from there you will see the heater around the fan. Check to see if this has visable blow marks on it. If so then it will need to be replaced.
If it looks ok you will need to remove it and test with a multi meter. But if the fan runs and the light comes on then 9 times out of 10 its the heater element at fault here.
If you need anymore info just get back to me.